INTRODUCTION. 19 



cies, the capability of copulating together, and of pro- 

 ducing thereby progeny that, in their turn, should prove 

 prolific. Camper, Daubenton, Pallas, Buffon, 

 Hunter, and other celebrated naturalists and physio- 

 logists of that time, adopted this criterion : but latter 

 observations have proved that this rule is by no means 

 infallible, and that it is in fact to be but little depended 

 on ; for, although hybrid animals for the most part do 

 not prove fruitful, yet it is sufficiently notorious that 

 instances do occur when even prolific offspring are 

 produced between parents of difierent species. The 

 mule has been known to cover the mare ; and, in warm 

 countries, it is not very uncommon for her to produce, 

 by this union, an animal that usually partakes less of 

 the mare than of the mule. In the East, the mule itself 

 has also been known to fecundate. The he-goat and 

 ewe have likewise, by their union, produced prolific 

 young ; and, among birds, similar instances are by no 

 means uncommon. From these, and numerous other 

 facts of a similar tendency, we are able analogically to 

 decide, that the capability of the dog to produce fruit- 

 ful off'spring, from sexual intercourse with any other 

 member of the canine genus, cannot be considered as 

 any proof of his being himself derived from such a 

 source. 



In addition to what has been advanced, it remains to 

 be added, that native breeds of wild dogs are still 

 found in some parts of the world, all of which present 

 one common character, particularly of the head and 

 face; and which character difi*ers considerably from 

 that of either the wolf, fox, or jackal. Further, it 

 may be remarked, that such dogs as had once been re- 

 claimed and made tame, but which from circumstances 

 had again become wild (however, during their subjuga- 



